1. Field of the Invention
The present invention relates to a saturable absorption type optical switch and a method for controlling the same.
2. Description of the Related Art
With reference to this kind of saturable absorption type optical switch, its operation theory is disclosed in Technical Digest of CPT' 98 (CPT' 98=International Topical Workshop on Contemporary Photonic Technologies), "Optical noise reduction by a semiconductor waveguide saturable absorber", Yoichi Hashimoto et al., pp 215-216, Jan. 12-14, 1998, in cooperation with IEICE Electronics Society & JSAP & IEEE-LEOS & OSA. However, its practical use has not been argued yet.
Moreover, technologies existing before the present invention was made generally employ an optical switch driven by application of a current or a voltage.
FIG. 1 is a block diagram showing an example of a conventional optical switch.
As shown in FIG. 1, the conventional optical switch comprises optical divider 101 for receiving a light signal to divide it into signals and outputting them; optical switch 102 for receiving one of the two signals outputted from optical divider 101 and outputting is as a light signal according to a control signal; receiving circuit 103 for receiving the other signal of the two signals outputted from optical divider 101 and extracting a component of the control signal from a signal applied thereto; and control circuit 104 for controlling optical switch 102 depending on the control signal extracted by receiving circuit 103.
In the optical switch constructed as described above, the control signal for driving optical switch 102 is superposed on the light signal, and the light signal including the control signal superposed thereon is divided by optical divider 101. The control signal component is extracted by receiving circuit 103, and control circuit 104 is controlled by the control signal extracted. Thus, optical switch 102 is controlled.
However, since the foregoing conventional optical switch needs a circuit for extracting the control signal and a control circuit for driving the optical switch, the above described conventional optical switch has a problem that a structure of the optical switch becomes complicated.